The pentacle is one of the most commonly used magical tools in the Wiccan religion, as well as in some traditions of Paganism. Typically, it is used on the altar as a place to hold items that are about to be ritually consecrated or charged. In some traditions, the pent represents the element of Earth.
There are many absolutely beautiful pentacles available commercially, made of wood, tile, metal, ceramic, and just about every other type of material. If you're operating on a budget, however, or if you just like the idea of handcrafting your own magical tools, it's not hard to make a pentacle of your own.
You'll need a wooden disc in the size of your choice, available at nearly any hardware or craft store. The one in the photo is a 7" circle, and cost less than $3.00. You'll also need to decide whether you want to paint your pentacle pattern, or burn it into the wood. The one in the photo is burned on, using a woodburning pen that I bought for $2.00 at a craft store. Finally, you'll need some clear polyeurethane and a brush.